*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    font-size: 14px;
}
li{
    list-style-type: none;
}
.puzzle{
    width: 322px;
    margin: 0 auto;
    margin-top: 3vw;
    text-align: center;
}
.game-box{
    width: 322px;
    height: 322px;
}
.game-box ul{
    width: 100%;
    height: 100%;
    border: 3px solid #333;
    border-radius: 4px;
    background: url(./bg.jpg) no-repeat center;
    background-size: cover;
}
.game-box ul.on{
    background: transparent;
    position: relative;
}
.game-reset{
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
}
.game-reset button{
    border: none;
    height: 30px;
    line-height: 30px;
    background-color: #eee;
    color: #333;
    padding: 0 15px;
    margin-right: 10px;
    cursor: pointer;
}
.game-reset .timer{
    display: inline-block;
    min-width: 20px;
    color: darkturquoise;
}
.game-box li{
    position: absolute;
    width: 100px;
    height: 100px;
    margin: 2.5px;
    background-image: url(./bg.jpg);
    background-repeat: no-repeat;
    background-size: 300px;
    cursor: pointer;
    transition: all .4s;
}
.game-box .game-box-1{
    background-position: 0 0;
}
.game-box .game-box-2{
    background-position: -100px 0;
}
.game-box .game-box-3{
    background-position: -200px 0;
}
.game-box .game-box-4{
    background-position: 0 -100px;
}
.game-box .game-box-5{
    background-position: -100px -100px;
}
.game-box .game-box-6{
    background-position: -200px -100px;
}
.game-box .game-box-7{
    background-position: 0 -200px;
}
.game-box .game-box-8{
    background-position: -100px -200px;
}
.game-box .game-box-9{
    background: cornsilk;
}